Displacement node adds unwanted spikes
This is apparently an AMD GPU problem.  Similar issues have been found apparently.  My condolences to anyone else out there on Team Red.
https://developer.blender.org/T77095
https://devtalk.blender.org/t/blender-2-83-crashing-on-amd-gpu/13641
Thanks to Rich and Christopher for the speedy and helpful replies!